Process for shifting a double bond in an olefinic hydrocarbon



United States Patent O PROCESS FOR SHIFIING A DOUBLE BOND IN AN OLEFINICHYDROCARBON Herbert R. Appell, North Riverside, 11]., assignor, by

mesne assignments, to Universal Oil Products Company, Des Plaines, 11].,a corporation of Delaware.

No Drawing. Filed Apr. 14, 1958, Ser. No. 728,096

6 Claims. (Cl. 260-6832) This invention relates to a process forshifting the double bond in an olefinic hydrocarbon to a more centrallylocated position therein, and more particularly relates to a process forshifting the double bond in a 1- olefin containing more than threecarbon atoms to a more centrally located position in said olefin, andstill more particularly relates to a process for the conversion ofl-butene to Z-butene.

The recent introduction of automobile engines of high compression ratioshas led to the need for the utilization of processes in the petroleumrefining industry for the production of extremely high antiknockhydrocarbons as fuels. One process for the production of such highantiknock hydrocarbons is the catalytic alkylation of isoparaflinhydrocarbons with olefins. In this alkylation process various catalyticagents have been suggested including concentrated sulfuric acid andliquid hydrogen fluoride. With these catalytic agents, for example, thealkylation of isobutane with four carbon atom olefin fractions orstreams has been practiced commercially on a Wide scale. There has beena general feeling in the practice of these alkylation processes,however, that utilization of Z-butene as the primary olefinichydrocarbon results in the productionof higher octane number alkylateproduct than does the utilization of l-butene. As the demand for higherand higher octane number motor fuels has increased, the necessity forthe development and utilization of a process for the conversion ofl-butene to Z-butene has widened. Various processes for such double bondshifting have been suggested in'the prior art. However, in the main,these processes have been relatively high temperature ones in which theshifting of the double bond has been limited by equilibriumconsiderations. It is an object of the present invention to provide aprocess which can be utilized at relatively low temperatures, in liquidor vapor phase as may be desired, and in a continuous manner for longperiods of time if so desired, to obtain equilibrium conversions ofl-olefins to olefins in which the double bond is more centrally located.In this manner the degree of branching of the product from the catalyticalkylation of'isoparafins with these olefins is increased. Thisincreased branching as is well known in the prior art results inincreased octane number of the alkylate product.

One embodiment of this invention relates to a processerating'temperatures in the neighborhood of about 150 for shifting thedouble bond in an olefinic hydrocarbon lyst comprising an alkali metaldisposed on a support, and recovering the resultant product;

Another embodiment of the present invention relates to a process forshifting the double bond in a l-olefin to a more centrally locatedposition therein which comprises subjecting said l-olefin to double bondisomerization at a temperature of from about 0 to about C. in thepresence of hydrogen and a catalyst comprising an alkali metal disposedon a precalcined high surface area support, and recovering the resultantproduct. A further embodiment of the present invention relates to aprocess for shifting the double bond in a l-olefin to a more centrallylocated position therein which comprises subjecting said l-olefin todouble bond isomerization at a temperature of from about '0 to about 100C. in the presence of hydrogen and a catalyst comprising sodium disposedon a precalcined high surface area alumina support, and recovering theresultant product. A specific embodiment of this invention relates to aprocess for shifting the double bond in l-butene to 2-butene whichcomprises subjecting said l-butene to double bond isomerization at atemperature of from about 0 to about 100 C. in the presence of hydrogenand a catalyst comprising sodium disposed on a precalcined high surfacearea alumina support, and recovering'the result ant product.

In the last few years the prior art has disclosed the use of alkalimetals as catalysts for various reactions including some hydrocarbonconversion reactions, more specifically, olefin isomerization reactions.This prior art, however, discloses minimum operable temperatures forthese reactions in the neighborhood of about C. In some instances theuse of extremely high pressures such as over 100 atmospheres has beendisclosed as necessary. Attempts to overcome the necessity for such highpressures has led to the discovery of the use of certain so-calledpromoters for thesealkali metals. However, while the use of suchpromoters has resulted in the dis covery that lower pressures areoperable, the use of op- C. or higher has still'been considerednecessary. It has recently been discovered that these operatingtemperatures can be substantially lowered by the simple expedient ofdisposing the alkali metal catalyst on a support, and that the resultantcomposite is effective for shifting the double bonds in olefins atrelatively moderate pressures in the absence of any added catalystpromoter. This discovery is important not only because of the economiesin necessary equipment which maybe achieved during the utilization ofthe process, but also because of equilibrium considerations. Forexample, utilizing 1-butene as the olefin, at 277 C. a conversion to 84%of Z-butene is maximum. A lowering of the reaction temperature to 27 canincrease this theoretical conversion per pass to greater thn 95% ofZ-butene. As set forth hereinabove, such an increase in Z-butene contentin an olefin stream utilized for reaction with an isoparaflin to producehigh octane number alkylate is extremely important from the octanenumber standpoint of the alkylate. Furthermore, alkali metals disposedon supports result in catalytic composites which can be utilized asfixed beds in reaction zones and which thus lend themselves to adoptionin processes of the so-called fixed bed typewhich are extremelydesirable for adoption on Patented Sept. s, 1960 ing alkali metalsdisposed on supports, however, have been found to sulfer from oneinherent disadvantage in spite of the fact that they are extremelyactive and can be utilized at the low temperatures set forthhereinabove. These catalytic composites tend to deactivate relativelyrapidly during use as a fixed bed for the isomerization of double bondsin olefinic hydrocarbons. It has now been discovered that thisdeactivation can be substantial- 1y reduced, or for all practicalpurposes eliminated, by, the. concurrent passage of hydrogen along withthe olefinic hydrocarbon being subjected to double bond iso-' men'zationover the catalyst comprising an alkali metal disposed on a support. Thisis surprising since the hydrogen apparently has no chemical effectduring the reaction and since the concurrent use thereof might beexpectedto saturate at least some of the double bonds present in. theolefinic hydrocarbon feed stock. However, such is not the case, and longcatalyst life has now been achieved in a most practical manner by thesimple expedient of hydrogen utilization. Since substantially nohydrogen is consumed in the reaction, the" hydrogen mayibereadilyseparated from the reaction products by well known means and recycled tothe reaction zone for reuse thereini. This outstanding feature of theprocess of the present invention will be described further in detailhereinafter.

The olefinic' hydrocarbons which are utilized in the process of thisinvention all contain more than three carbon atoms and may be derivedfrom various sources. As pointed out hereinabove, the process of thepresent invention is particularly suited for or adapted to conversionof. l-butene to 2-butene. The l-butene may be charged to the process ofthis invention in pure form or in admixture with other hydrocarbonsincluding any or all of 2-butene, isobutylene, normal butane, isobutane,etc; By the proper balance of the isobutane content of such a mixture,it will be recognized'that the mixture may be a typical alkylation feedstock. Thus, the process of the present invention maybe utilized for theconversion of the l-butene content in an alkylation feed stock to2-butene prior to utilization of the feed stock in the alkylationreaction. The process of the present invention can likewise be utilizedfor shifting of the double'bond in n-amylenes or isoamylenes to pro duceamylenes in which the double bond is in a more centrally locatedposition. Likewise, hexenes such as l-hexene or 2-hexene can beconverted to 2- or 3-hexene by utilization of the process of thisinvention. This double bond shifting reaction of l-olefins oralpha-olefins to olefins in which the double bond is in a more centrallylocated position is readily adaptable tomany feed stocks as disclosd inthe prior art. For example, the process may be utilized with feed stockscomprising l-olefi'ns such as l-pentene, .l-hexene, l-heptene, loctene,l-nonene, l-decene, I-undecene, I-dodecene, 1- tridecene, l-tetradecene,I-pentadecene, etc., Z-metbyll-butene, S-methyl-l-butene,2-methyl-1-pentene, 3-'meth yl-l-pentene, 4-methyl-l-pentene, Z-methyl-lhexene, 3- methyl-l-hexene, 4-methyl-1-hexene, '5-methyl-1-hexene,2-methyl-2-hexene, 3-methyl-3-hexene, 4-methyl'-3-hexene,5-methyl-3-hexene, 2-methyl-l-heptene, 3 -met-hyl-l'- heptene,4-methyl-l-heptene, 5-methyl-l-heptene, 6-methyl-l-heptene,2-methyl-2-heptene, 3'-methyl-2-heptene, 4 methyl-Z-heptene,S-methyI-Z-heptene, 6-methyl-2-heptene, Z-methyl-l-octene,S-methyl-l-octene, 4-methyl1- octene, S-methyl-l-octene,o-methyld-oct'ene, 7-methyll-octene, etc 'While the present invention isdiscussed in detail in relation to the shifting of the double bond inl-butene to produce Z-butene, this discussion -is intro duced merely forthe purpose of convenience and with i no intention of limiting' theolefinic hydrocarbons which can be converted in accordance withthisprocess.

a As set forth hereinabove; the process for shift g i e aosa'na doublebond in an olefinic hydrocarbon to a more centrally located position inan olefinic hydrocarbon is effected in the presence of hydrogen and inthe presence of an alkali metal catalyst. The alkali metal catalystsutilizable in the process are selected from the group consisting oflithium, sodium, potassium, rubidium, and cesium, or mixtures thereof.Of these alkali metals, the more plentiful and less expensive sodium andpotassium are preferred, either alone or in admixture with one another.These alkali metals are disposed on a support in a quantity ranging fromabout 2% to about 30% by Weight based on the support. Not every supportcan be utilized as a satisfactory one for disposal of an alkali metalthereon. As is'wellknown, the metals to: act violently with water andthus care mustbe taken to utilize a support which is relatively orsubstantially free from water. In most cases this freedom from water ofthe support is achieved by precalcination of the support.

, This precalcination is'usua'lly carried out at relatively hightemperature,'for example, in the range of from about 400 to about 700 C.and for a time sufficient to effect substantial removal of adsorbed orcombined water from the support. These times will vary depending uponthe support, and depending upon whether the water is in a combined or inmerely a physically'adsorbed form. In addition to the necessity forfreedom from Water, the support is additionally characterized in thenecessity for having a 'high surface area. By'the term high surface areais meant a surfacearea measured by adsorption techniques within therange of from about 25 toabout 500' or more square meters per gram. Forexample, it has been found that certain low surface area supports suchas alpha-alumina which is obviously free from combined Waterland whichhas been freed from adsorbed water is not a satisfactory support for thealkali metals in the preparation of: the catalysts for use in theprocess of this invention. Alpha-alumina is characterized by' a surfacearea ranging from about 10 to about 25 square meters per gram. Incontrast to alpha-alumina, gamma-alumina which has a surface arearanging from about to about. 300 square meters per gram, and which hasbeen freed from adsorbed water, and which contains no combined water, isa satisfactory support. Celite, a naturally occurring mineral, afterprecal'cination, is not a. satisfactory support. Celite has a surfacearea of from about 2 to about lO-square meters per gram. Like wise,alkali metal dispersions on sand or other'low surface' area silicas arenot satisfactory catalysts in this process. Inaddition, aluminas whichcontain combined water but which have relatively high surface area arealso not satisfactory supports.- -Such aluminas include dried aluminamonohydrates which have not been sufficiently calcined to removecombined water and to' form gamma-alumina. These alumina hydrates, mayhave surface areas ranging from about 50 to about 200 square meters pergram but because they contain combinedwater are not satisfactorysupports. Particularly preferred supports for use in preparationof'catalysts utilized in the process of this invention include high surfacearea crystalline alumina modifications such'as gamma-alumina andtheta-alumina, high surface area silica, charcoaIs, magnesia,silica-alumina, -silica-alumina-magnesia,. etc. However, as is obvious.from the above discussion, the limitation of the use of any particularsupport is one of freedom from combined or adsorbed water in combinationwith the'surface area of the selected support.

The alkali metal may- 'bel'disposed. on a support in any suitable mannerfQne manner: which has been found particularly advantageousisvaporization of the alkali metal and passage of. the vapors over thesupport. In this manner of preparation: care must be taken to utilizerelatively low temperatures since heat is givenaoif onicontact of thealka1i'meta1 with the support and since high temperatures tendto destroythe amount of surface in the support, and may also cause certainchemical reactions of the support with the alkali metals which aredetrimental to catalytic activity. Sodium melts at about 97 C. and inimpregnating a selected support with sodium it is preferred to carry outthe impregnation or disposal of the sodium thereon at temperatures inthe range of from about 100 to about 150 C. This can be accomplished,for example, by melting sodium and dropping the molten sodium on thesupport or by passage of a stream of inert gas such as nitrogen or argonthrough the molten sodium and over a bed of the selected supportdisposed in a separate zone maintained at the desired temperature withcooling or heating means connected therewith. Potassium melts at about62 C. and thus the impregnation of a selected support with potassium canhe carried out at lower temperatures. Potassium disposed on one of theabove mentioned supports appears to be a more active catalyst for thereactions disclosed herein than does sodium and this difierence inactivity may be due to the lower temperatures which can be used in thedisposal of potassium on the support. Supported lithium catalysts appearto be less active and this may be a reflection of the higher meltingpoint of lithium, 186 C., and the higher temperatures which must occuron contact of the lithium with the support. Furthermore, disposal of theselected alkali metal on the support must be carried out in a manner sothat the high surface area of the support in combination with the alkalimetal is not destroyed by incorporation of excess quantifies of thealkali metal therein. In other words, the pores and passage ways of thesupport can be filled and blocked by the addition of excess quantifiesof the alkali metal. This is obviously undesirable and supported alkalimetals containing excess alkali metal are likewise inactive in theprocess.

As set forth hereinabove, catalysts of the alkali metal type disposed ona support and prepared in the manner described may be utilized in theprocess in a manner which enables the process to be carried out atso-called mild operating conditions. As set forth hereinabove, the thusprepared catalysts are particularly adapted for use in so-called fixedbed processes. The double bond shifting reaction of the presentinvention can'thus be carried out in the presence of these catalysts attemperatures in the range of from about to about 100 C. and at pressuresranging from atmospheric to about 100 pounds per square inch or more.Pressure does not appear to be a critical variable in the process sincethe conversion reaction may be carried out in either liquid phase orvapor phase. Thus, the pressure utilized may he selected purely from themost advantageous pressure based upon economic considerations and uponthe stability of the particular olefinic hydrocarbon charged to theprocess under the necessary processing conditions. In carrying out theprocess of this invention in a continuous manner, hourly liquid spacevelocities based upon the quantity of olefinic hydrocarbon charged maybe varied within the relatively wide range of from about 0.1 to about 20or more, equilibrium conversions being attained within the range of fromabout 0.1 to about 10. If equilibrium conversion of the olefinichydrocarbon to the double bond isomer thereof is not necessary, higherspace velocities may be utilized to attain the preselected approach toequilibrium conversion.

The attainment of the desired shifting of the double bond in an olefinichydrocarbon to a more centrally lo cated position is accomplished by theprocess of the present'invention in the absence of so-called alkalimetal catalyst promoters as taught by the prior art. These promotersinclude organic compounds capable of reacting with a portion of thealkali metal and forming organometallic compounds in situ during theresidence time of the-reactants in the reaction zone in the presence ofthe metal. Heretofore it has been considered necessary to utilize suchpromoters to carryout the process of this invention at so-calledmoderate pressures and tem-,

peratures. As set torth hereinabove, it has now been found that suchpromoters are not needed and that the reaction may be carried out atrelatively low pressures and temperatures by utilization of the alkalimetal 'disposed on a preselected support.

In utilizing these catalytic composites comprising alkali metalsdisposed on supports at low temperature conditions, at moderatepressures, and at space velocities preselected for desired conversion,one deficiency in their ability to promote the process has been noted.These, supported alkali metal catalytic composites are all ex-. tremelyactive initially. However, in use they tend to lose some of thisactivity for reasons which are not understood. For example, a catalystcomposite comprising sodium disposed on alumina which gives equilibriumcon-. version of l-butene to Z-butene at room temperature, at 300p.s.-i.g., and at 16 hourly liquid space velocity, decreases in activityto about one-half of its original activity in a relatively short periodof time. This decrease in actiw'ty is, of course, undesirable when anattempt is made to utilize these catalytic composites commercially sincesuitable commercial catalytic composites must not only exhibit desiredactivity but must also have the property of relatively long life in use.This is particularly true of so-called fixed bed type catalysts where itbecomes necessary to open reactors, remove spent catalyst, and replacethe same. As is readily apparent to one skilled in the art, these stepsrequire time which could otherwise be utilized for additionalprocessing. As set 'forth hereinabove, it has now been found that theinitial activity ofthese catalytic composites can' be substantiallyretained during long periods of use when the processing of the olefinichydrocarbon over these catalytic composites is conducted in a hydrogenatmosphere. The quantity of hydrogen utilized along with the olefinichydrocarbons does not appear to be critical and thus may vary over arelatively wide range of from about 0.01 to about 10 mole of hydrogenper'mol' of olefinic hydrocarbon. As is 'the case with pressurediscussed hereinabove, the selection of the exact amount of hydrogenutilized can be based on economic'considerations. This hydrogenmay beintroduced along with the olefinic hydrocarbon or may be introduced atmultipoiuts in the reactor and its desirable effect maintained undereither processing scheme. Furthermore, it has been found that passage ofhydrogen over previously deactivated catalytic composites comprisingalkali metal disposed on a support tends to reactivate the catalyst andthat this reactivated catalyst may be successfully utilized forprocessing as herein discussed. For example, these supported alkalimetal catalysts are useful catalysts for polymerization reactions, suchas the polymerization of ethylene or isobutylene. After such use theiractivity for the double bond shifting reaction in the process of thepresent invention is decreased. This activity can be restored to a highlevel and these catalysts utilized for long periods of time by thesimple expedient of treating the thus deactivated composite withhydrogen and then utilizing hydrogen along with the olefinic hydrocarbonbeing charged to the process in accordance with the present invention.After passage of the olefinic drocarbon and hydrogen over a bed of thiscatalyst com-, posite, the hydrogen may -be separated from the olefinichydrocarbon by means well known in the art including high pressureseparation, flashing under pressure, by fractionation, etc. The hydrogenwhich is thus recovered. is then compressed to a preselected pressureand may again be recycled and reused in this process. Hydrogen consumption by reaction with the olefinic hydrocarbon in this process isfor all practical purposes negligible. Most hydrogen loss is due tosolubility in the hydrocarbons after processing and thus it has beenfound that makeup hydrogen is usually needed only in an amount tobalance that which is soluble in the hydrocarbons under the con- 7ditions of temperature and. pressure utilized for the separation of thehydrogen from the hydrocarbons. The hydrogen utilized maybe in pure formor it may be diluted with various inert materials including nitrogen,methane,

ethane, etc, which have little or no effect on the reaction or upon thecatalytic composite comprising an alkali metal disposed on a support;Incornmercial refinery operations such hydrogenis readily available as abyproduct from. catalytic reforming; for example. suchhyd-rogen usuallycontains minor quantities of oxygenated compounds or hydrogen sulfide,it is usually advisable to purify the same for the removal of suchimpurities which will react with or deactivate the presently disclosedcatalytic composites.

The following examples are introduced for the purpose of illustration ofspecific embodiments of this invention but with no intention of undulylimiting the above disclosed generally broad scope of this invention.

EXAMPLE I 1 This example was carried out and is described herein for.comparative purposes. The catalyst utilized in this experiment was 16.6%sodium disposed on alumina. The alumina utilized was in the form of inchspheres which had been precalcined at 650 C. in a nitrogen atmosphere toinsure freedom from adsorbed and combined water. These alumina spheresafter calcination had a surface area of about 180 square meters per gramand an apparent bulk density of about 0.5 grams per milliliter. X-raydiifraction analyses showed that they were substantially anhydrousgamma-alumina.

The disposal of sodium on these gamma-alumina spheres is carried out byplacing the spheres in a glass flask equipped with heating and stirringmeans. The flask is purged with nitrogen to insure freedom from air. Thetemperature of the spheres is then raised to about 150-170? C., andsufficient molten sodium added thereto during stirring to attain thedesired sodium content on the spheres. As stated above, these spheresafter preparation contained 16.6% by weight of sodium.

-.A sample of the above spheres, 100 milliliters, was placed as a fixedbed in a reaction tube in a bench scale plant. The bench scale plantcontained as auxiliary equipment, pumps, heating and cooling means forthe reaction tube, product collection vessels for both gaseous andliquid products, and product removal means. This particular experimentwas carried out at 300 p.s.i.g., approximately 16J0 hourly liquid spacevelocity, and with no heating or cooling of the reaction tube. Thetemperature was allowed to seek its own level in the catalyst bed andthe hot spot in the bed produced by the reaction was followed as well asthe average catalyst temperature. TheJfeed. stock used in thisexperiment was technical kbutene.

This experiment was divided into four periods, the first three of onehour duration each, and the last period of one-half hour duration. Theanalyses which are presented hereinafter for eachper-iod were obtainedfrom the product for the last 7 /2 minutes of each period. In period 1 ahot spot was observed in the catalyst bed, the

7 temperature reaching 86 C. This obviously indicates high initialcatalyst activity. The average catalyst temperature attained was 50 C.The product analysis from period 1 is as follows: l-butene, 9.2 molpercent; cis-2- butene, 35.6 mol percent; trans-Z-butene, 52.4 molpercent; and 2.8 mol percent other materials to balance. This resultshows that conversion to equilibrium is readily attained. By period 2the peak catalyst temperature had already dropped to 80 C. and theaverage catalyst temperature'was 42 C. The analysis of' the product from2 is as follows:' lbutene, 33.4 mol percent; cis-2- butene, 54.6 molpercent; trans-2-butene,-10.9 mol percent; and 1.1 mol percent othermaterials to balance. This result from the end of period 2 shows thatthe cat- Howeyer, since alyst is already declining in conversionactivity. Not only is the l-hutene content of this product high, but thecis to trans ratio in the 2-butene portion of the product is higher thanthe equilibrium figure. During period 3 the peak catalyst temperatureagain dropped to 53 C. and the average catalyst temperature wasl37 C.The product analysis at thelend of period 3 is as follows: l-butene,46.7 mol percent; cis-2-butene,- 44.2 mol percent; trans-2- butene, 7. 5mol percent; and 1.6 mol percent'other ma terials to balance. This againshows the catalyst is rapidly declining in activity, the l-bu-tenecontent of the eflluent having risen again and the cis to trans ratio ofthe product still going higher. Period 4 was continued for only one-halfhour since the supply of l-butene was rapidly diminishing. During theperiod, the peak tem: perature attained was 44 C. and the averagecatalyst temperature was 32 C. The analysis of the eflluent for the last7 /2 minutes of this one-half hour period is as follows: l-butene, 55.2mol percent; cis-2-butene, 38.9 mol percent; trans-2-butene, 5.4 molpercent; and 0.5 other materials to balance. Here again, the 1-butenecontent of the efiluent is higher as is the cis to trans ratio of theZ-butene portion of the product. 7

This example and experiment illustrate that sodium disposed on aluminais an olefin isomerizationcatalyst but that the activity ofthis catalystrapidly decreases in use in the absence of added hydrogen. This effectof added hydrogen will be set forth in the following examples. 7

EXAMPLE II In this example another 100 milliliter sample of the 16.6weight percent sodium disposed on alumina described in Example I wasutilized. This experiment was carried out in the same equipmentdescribed in Example I. The feedstock again was technical l-butene.Conditions utilized in this example again include ambient tem-'perature, 300 p.s.i.g. and about 16.0 hourly liquid space velocity forperiods 1 and 2, and O p.s.i.g. and 0.85 hour'- ly liquid space velocityfor periods 3 and 4. During this experiment there was addedapproximately 0.36 cubic feet per hour of hydrogen. Prior to use thiscatalyst was treated with hydrogen at 200 C., 300 p.s.i.g., for twohours. a

Period 1 had a duration'of 30 minutes and a catalyst hot spot of 86 C.was observed. This catalyst hot spot corresponds to that observed duringperiod lin Example I. No analysis of the period 1 product was obtained.The product from period 2 which had a duration of 7.5 minutes wasanalyzed. In contrast to period 2 in Example I, during which thecatalyst peak temperature dropped to (3., indicating loss in catalystactivity, the catalyst peak temperature for the period 2 remained at 86C. The productanalysis is as follows: l-butene, 9.0 mol percent;cis-2-butene, 37.9 mol percent; trans-2-butene, 52.2 mol percent; and0.9 mol percent other materials to balance. From the maintenance of thepeak temperature in the catalyst bed and from the fact that conversionis main tained' at a high level at the end of period 2,'it is obviousthat the presence of hydrogen results in the process being stabilized.In experiments in which hydrogen is not added, a relatively rapiddecline in peak temperature with time occurs as well as a deteriorationof product quality.

At this point the process conditions were changed to 0 p.s.i.g. and anhourly liquid space velocity of 0.85. The drop in pressure results inthe reaction system changing from liquid phase to vapor phase operation.Period 3 was carried out for one hour and 20 minutes duration duringwhich time the catalyst hot spot decreased to 36 C. and remained there.Then, period 4 was carried out for 15 minutes during which time theefiiuentwas .collected'for analysis; During period 4 the catalyst peaktemperature remained at 36 C., the same as had been .'9' observed inperiod 3. The analysis of the product from period 4 is as follows:l-butene, 6.9 mol percent; cis-2- butene, 33.5 mol percent;trans-Z-butene, 59.1 mol percent; and 0.5 mol percent other materials tobalance.

From the analysis of the eflluent from period 4 it is obvious that thecatalyst has maintained its activity through the change from liquidphase to vapor phase and over the additional hour and 35 minutesprocessing period. Equilibrium conversion of l-butene -to 2-buteneisomers was attained at the end of period 4 even though the peakcatalyst temperature was 36 C. This is indicative of exceptionally highcatalyst activity EXAMPLE III This example illustrates the utilizationof a catalyst comprising sodium disposed on alumina without hydrogenaddition, with hydrogen reactivation between periods, and then thestabilization of catalyst activity by the utilization of additionalhydrogen during processing. The experiment described in this example wascarried out in the same apparatus described hereinabove in Example I.

In this example a catalyst was prepared utilizing 45.7 grams of the samegamma-alumina described in Example l which had been calcined at 650 C.Since this gammaalumina had been kept in storage, prior to use in thecatalyst preparation, it was calcined at 500 C. to remove adsorbedwater. This calcined and dried alumina was poured while hot into a glassflask equipped with heating and stirring means. Nitrogen was passedthrough the flask to flush out air and when the temperature of thealumina being stirred cooled to about 100 C., 5 grams of molten sodiumwere added batchwise in three portions. Stirring was continued until allof the sodium was absorbed by the alumina. The catalyst was uniformlydarkat completion and contained 9.8 weight percent This catalyst,comprising 100 milliliters, was then placed as a fixed bed in thereaction tube. The temperature of the mass was raised to about 100 C.and hydrogen passed therethrough for two hours at 300 p.s.i.g.--Processing conditions utilized in this experiment include 300 p.s.i.g.,approximately 16 hourly liquid space velocity, and no heating or coolingon the reactor so that the temperatures attained during reaction wouldbe indicative of the amount of heat given off and thus catalystactivity. The feed stock utilized was technical l-butene. Period 1 ofthis experiment was carried out for 30 minutes during which time anaverage catalyst temperature of 66 C. and a peak catalyst temperature of94 C. were attained. Then, period 2 was started and the productcollected for 7 minutes. The efliuent from period 2 analyzed as follows:l-butene, 33.7 mol percent; cis-2-butene, 36.9 mol percent;trans-Z-butene, 26.5 mol percent; and other materials'to balance, 2.9mol percent. During; period 2 it was noted that the average catalysttemperature dropped 3 C. although the peak temperature re'mainedthe.same at 94 .C.

Since the activity of this catalyst did not result in the attainment ofequilibrium conversion, an attempt was made to activate or' reactivatethesame by a treatment with hydrogen. Therefore, hydrogen was againpassed over the catalyst for two hours at 100 C. in the absence ofhydrocarbons. Period 3 was then carried out for 30 minutes time and anaverage catalyst temperature of 61 C. and a peak catalyst temperature of82 C. were observed. Then, another test for analysis of 7 /2 minutesduration was started. The results of the analysis of the period 4reaction zone efliuent are as follows: l-butene, 35.9 mol percent;cis-2-butene, 42.6 mol percent; trans-2-butene, 16.2 mol percent; andother materials to balance, 5.3 mol percent. During period 4 the averagecatalyst temperature again dropped, this time to 57 C., and the peakcatalyst temperature observed 10 was 81 (3. From the gradual decline inpeak catalyst temperatures, and from the fact that the cisto trans-2-butene ratio was increasing, it was apparent that the activity of thecatalyst was not stabilized. Prior to period 5, hydrocarbons wereremoved from the plant and the catalyst was treated with hydrogen fortwo hours at 200 C. in an attempt to reactivate and stabilize the same.Period 5 was carried out for 30 minutes time during which an averagecatalyst temperature of C. and a peak catalyst temperature of 84 C. wasobserved. Then, period 6 was carried out for 7 /2 min utes and theproduct collected and analyzed. This analynot is as follows; l-butene,24.5 mol percent; cis-2-butene, 40.3 mol percent; trans-Z-butene, 17.5mol percent; and other materials to balance, 1.4 mol percent. Duringperiod 6 the average catalyst temperature declined to 58 C. from the 80C. observed during period 5, but the peak temperature only declined to81 C. from the 84 C. observed in period 5. It was again obvious that thecatalyst did not have a stable activity.

Therefore, the catalyst was again treated with hydrogen for two hours at200 C. and during periods 7 and 8, 0.36 cubic feet of hydrogen per hourwas added along with the hydrocarbon feed. During period 7, which lastedfor one-half hour, the average catalyst temperature was 41 C. and thepeak catalyst temperature was 78 C. Period 8 was another 7 /2 minutetest carried out to ob-, tain product for analysis. Analysis of theperiod 8 product is as follows: l-butene, 24.5 mol percent;cis-2-butene, 56.4 mol percent; and trans-Z-butene, 19.1 mol percent.During period 8 the average catalyst temperature was 42 C. whichindicates maintenance of activity through periods 7 and 8. Likewise, thepeak catalyst temperature remained at 78 C., the same as had been forperiod 7. These last two results indicate that the activity of thecatalyst is stabilized by the addition of hydrogen during processing.Further-more, comparison of the results from period 8 with thoseobtained from periods 2, 4, and 6 show'that'the catalyst was not onlystable during periods 7 and 8, but was also more active for the doublebond shifting reaction of the present invention, in particular theconversion of l-butene to 2-butene.

EXAMPLE IV This example illustrates the utilization of a catalystcomprising sodium disposed on alumina for the double bond shifting ofl-butene to 2-butene in the presence of hydrogen. In this example thefeed utilized was a commercial C fraction analyzing as follows: propane,3.3 mol percent; propylene, 0.9 mol percent; isobutane, 27.8,molpercent; normal butane, 34.3 mol percent; l-butene, 7.5 mole percent;isobutylene, 8.7 mol percent; cis 2-bu-' t ene,.6.6 mol percent;trans-Z-butene, 9.4 mol percent; and 2-methylbutane, 1.5 mol percent. Inthis example another milliliters of the same catalyst described inExample I was utilized. This catalyst comprises 16.6% sodium disposed oninch gamma-alumina spheres which have been precalcined at 650 C. Priorto use, the feed was purified by passage through a scrubber containingsodium-potassium alloy. This experiment was carried out at 300 p.s.i.g.,approximately 16 hourly liquid space velocity, and no heating or coolingof the reaction tube. Here again, the temperature was allowed to seekits own level in the catalyst bed. Since the l-butene content of thefeed is low, very little, if any, heat was given OE and thus thetemperature remained constant at about 25 C. all through the variousprocessing periods. Each processing period was of a one hour durationand the product from the last 7 /2 minutes of each hour was collectedand analyzed. During the experiment hydrogen addition was maintainedconstant at about 0.40 cubic feet of hydrogen per hour. The results ofthe analyses for the last 7% minutes of each period are presented in thefollowing table.

means ii A 7 Table I ISOMERIZA'IION OF LBUTENE TO Z-BUTENE IN ACOMMERCIAL C(FRACTION IN THE PRESENCE OF HYDROGEN AND ALUMINA CONTAINING16.6% SODIUM- M01 Period Feed percent of feed j Propane 3.3 3.3 3.1 3.43.2 2.8 2.7 2.9 3.2 2.9 2.9

34. 3 36. 5 34. 9 34. 3 35. 5 35.1 34. 5 33. 7 34. 6 35.1 85. 5 7.5 3.02.3 2.2 1.8 1.7 2.2 2.0 1.2 '1.4 2.8 8.7 6.5 7.6 8.0 8.3 8.5 8.2 8.5 9.79.3 6.3 9. 4 10. 7 l1. 3. 11.0 10. 9 11. 7 11. 5 11. 3 11.0 11. 3 11.2Gls-2-butene 6. 6 9. 2 9.6 9. 3 9.8 10. 4 10.6 10. 2 9. 8 9. 9 10. 0ZmethyIbutane 1.5 1.7 1.5 1.4 2.1 2.5 1.9 1.9 1.1 1.1' 1.2

observed. Some of the l-butene converted to trans-2-' butene since theproduct analyses show about 11' mol percent trans-Z-butene in comparisonto about 9.5 mol percent in the feed. These'results show the operabilityof the process of the present invention and that the presence ofhydrogen stabilizes the catalyst sothat the activity does not descreasewith time. These results are accomplished without substantial change inany of the other components in the commercial 0.; fraction. Theresultant C fraction produced by the process of this invention is moresuitable as a feed stock for the alkylation of isobutane with butenessince the higher 2-butene content of the product will result in'analkylate having a higher octane number.

E? I claim as my invention:

1. A process for shifting the double bond in an olefinic hydrocarbon toa more centrally located position therein which comprises subjectingsaid olefinic hydrocarbon to double bond isomerizationat a temperatureof from about 0 to about 100 C. in the presence of from about 0.01 toabout 10 mols of added hydrogen per mol of olefin and a catalystcomprising an alkali metal disposed on a substantially anhydrous supporthaving a surface area of from about to about 500 square meters per gram,and recovering the resultant product.

2.A process for shifting the double bond in a l-olefin tjola morecentrally located position therein which comprises-subjecting saidl-olefin to double bond isomerization at a temperatureof from about 0 toabout 100 C.- i'irthe presence of from about 0.01 to about 10.mols ofadded hydrogen'per mol of olefin and a catalyst comprising an alkalimetal disposed on a substantially anhydrous support having a surfacearea of from about 25. to about 500 square meters per gram, andrecovering the resultant product. 7 V

3. A process for shifting the double bond in a .l-ole'fin to a morecentrally located position therein which comprises-subjecting saidl-olefin to double bond isomerization at a temperature of from about 0to about 100 C.

4. A process for shifting the double bond ina 11.-olefin to a morecentrally located position therein which comprises subjecting said.l-olefin to double bond isomerization at a temperature of from about 0to about C. in the presence of from about 0.01 toabout 10 mols of addedhydrogen per molofolefinand a catalyst com prising an alkali metaldisposed on a substantially auhydrous alumina support having a surfaceareaof from about 25 to about 500 square meters per gram, and.recovering the resultant product. p V 5. A process for shifting the.double bond in a l-olefin to a more centrally located position thereinwhich comprises subjecting said l-olefin to. double bond isomerizationat a, temperature of from about 0 to about 100 C. in the presence offrom about 0.01 to about 10 mols of added hydrogen per mol of olefin anda catalyst comprising an alkali metal disposed on a substantiallyanhydrous charcoal support having a surface area of' from about 25 toabout 500square meters per gram, andrecovering the resultant'product. 6.A process for shifting the double bond in l-butene to 2-butene whichcomprises subjecting said l-butene to double bond isomerization at. atemperature of from about 0 to about 100 C. in the presence of fromabout 0.01 to about 10 mols of added hydrogen per molof olefin and acatalyst comprising an alkali metal disposed on a substantiallyanhydrous area alumina support having a surface area of from. about 25to about 500 square meters per gram, and recovering the resultantproduct.

References Cited in the file of this patent UNITED STATES PATENTS2,375,687

OTHER I REFERENCES J.A.C.S.,'vol. 77, pp. 341 and 34s, Ian."20, '1955.

1. A PROCESS FOR SHIFTING THE DOUBLE BOND IN AN OLE FINIC HYDROCARBON TOA MORE CENTRALLY LOCATED POSITION THEREIN WHICH COMPRISES SUBJECTINGSAID OLEFINIC HYDROCARBON TO DOUBLE BOND ISOMERIZATION AT A TEMPERATUREOF FROM ABOUT 0* TO ABOUT 100*C. IN THE PRESENCE OF FROM ABOUT 0.01 TOABOUT 10 MOLS OF ADDED HYDROGEN PER MOL OF OLEFIN AND A CATALYSTCOMPRISING AN ALKALI METAL DISPOSED ON A SUBSTANTIALLY ANHYDROUS SUPPORTHAVING A SURFACE AREA OF FROM ABOUT 25 TO ABOUT 500 SQUARE METERS PERGRAM, AND RECOVERING THE RESULTANT PRODUCT.